In my earlier U.S. Pat. No. 4,681,401, an effective improved thin surface marking strip for adhering to a road surface or the like is disclosed embodying novel somewhat flattened, saw-tooth wedges provided with retroreflective material and of preferably substantially trapezoidal shape in longitudinal vertical section with rather critical separations between the wedges relative to height and width of the wedges to obviate shadowing effects, as in sunlight, in order to provide improved daylight observation and to increase effectiveness and life, particularly under conditions of rain-covered surfaces. Earlier art dealing with this type of technology is also disclosed in U.S. Pat. Nos. 4,236,788; 4,069,787; 4,040,760; 3,920,346; 3,587,415; and 3,399,607; 2,268,538 and 2,232,023.
While the marker strips of my said earlier patent and those in copending applications bearing Ser. Nos. 283,192, filed Dec. 12, 1988, now U.S. Pat. No. 4,969,713, issued Nov. 13, 1990 and 309,312 filed Feb. 10, 1989, and of common assignee herewith, have been particularly promising, certain difficulties have been encountered under more strenuous conditions of daylight use during low sun angles and at night with high levels of overhead ambient lighting, with regard to preventing the obscuring of the strips by the shadows cast under such lighting conditions. In addition, some of the earlier marker strips proved very complex to manufacture on a practical basis and did not, in practice, always provide sufficiently brilliant long range visibility by automobile headlamps at night, especially in the rain.